RESULTSIn normal subjects serum albumin concentration showed a significant decrease of 1.9 (95% CI 1.0 to 2.9) g/l by 7 weeks gestation with a further 8.2 (95% CI 7.5 to 8.9) g/l decrease by 36 weeks gestation, an overall change of 22%. Plasma volume first increased significantly by 190 (95% CI 105 to 275) ml between 7 and 12 weeks, with a further increase of 1003 (95% CI 871 to 1135) ml between 12 and 36 weeks of pregnancy, a change of 53%. The intravascular mass of albumin showed no change between non-pregnant, 7 and 12 week values but there was a significant rise of 19.5 (95% CI 15.1 to 23.9) g between 12 and 28 weeks of gestation, an overall increase of 19%. Diabetic subjects showed similar changes.